The difference between the two channels of EEG collected by BIS #557

Hello dear professor.

I would like to ask, what is the difference and purpose of the two EEG signals in vitalDB data? I don't quite understand how the two signals EEG1 and EEG2 obtained by BIS are used.

Hope to get your reply. Thank you very much.

 I wish you success in your work and good health.